Sterols of Glaucocystophytes

Abstract

Glaucocystophytes are a group of evolutionarily important freshwater algae that have an almost intact cyanobacterium, referred to as a cyanelle, as the photosynthetic organelle. Because of this, they have been the subject of a large number of studies over the past few decades on how a cyanobacterium transitioned into a chloroplast. However, studies on their lipid composition have lagged behind those on other areas of glaucocystophyte cell biology. To this end, we have examined the sterol composition of Cyanophora paradoxa Korshikov and Glaucocystis nostochinearum Itzigsohn in order to identify sterols left unidentified in previous studies. We have found that two isolates of G. nostochinearum and one of C. paradoxa uniformly produced three sterols: 24-methylcholest-5-en3b-ol, 24-ethylcholesta-5,22E-dien-3b-ol, and 24-ethylcholest-5-en-3b-ol.

Algal lipids, fatty acids and sterols

“…Among macroalgae, cholesterol is the dominant sterol in all the Rhodophyta, fucosterol in Phaeophyta, while the dominant sterol seems to vary within the orders among Chlorophyta (Al Easa et al , 1995) such as isofucosterol in Ulvales and clionasterol in Bryopsidales and Siphonocladales. Among microalgae, Haptophytes are characterized by the presence of unusual dihydroxysterols (pavlovols), pelagophytic algae by 24-propylidenecholesterol, diatoms by 4-desmethyl-23,24-dimethyl steroids, chlororachinophytes by crinosterols, stigmasterols, dinophytes by dinosterols and dinostanols except for the Kareniaceae members and Polarella glacialis (Leblond et al , 2003;Leblond et al , 2005;Leblond et al , 2011;Mooney et al , 2007;Thomson et al , 2004;Volkman et al , 1997). These algal sterols possess benefi cial healthpromoting effects such as hypercholesterolemic, antioxidant, anticancer, antidiabetic, antihypertensive, anti-infl ammatory responses (refer to the review by Kim and Ta, 2011).…”

Sterol Composition and Biosynthetic Genes of Vitrella brassicaformis, a Recently Discovered Chromerid: Comparison to Chromera velia and Phylogenetic Relationship with Apicomplexan Parasites

“…However, several classes of algae, such as glaucocystophytes (Leblond et al. ), chlorophytes (as reviewed by Volkman ), chlorarachniophytes (Leblond et al. ), have been reported to produce 24‐ethylcholest‐5‐en‐3β‐ol.…”

“…Rhodophytes, the predicted ancestor of chromerid plastids, typically produce cholesterol and several other sterols, such 5a-cholestan-3b-ol (cholestanol), cholesta-5,24-diene-3b-ol (desmosterol), cholest-5,7-dien-3b-ol (dehydrocholesterol) (Patterson 1991), that are different from the sterols produced by V. brassicaformis and C. velia. However, several classes of algae, such as glaucocystophytes (Leblond et al 2011), chlorophytes (as reviewed by Volkman 1986), chlorarachniophytes (Leblond et al 2005), have been reported to produce 24-ethylcholest-5-en-3b-ol. The MEP pathway (Rohmer et al 1996) is commonly found in eubacteria, green algae, and the chloroplasts of higher plants (Kuzuyama 2002;Lohr et al 2012), although a more comprehen- Figure 6 Maximum likelihood tree generated by using RAxML with LG+G model for isopentenyl diphosphate isomerase (IDI) protein sequence.…”

“…Vitrella brassicaformis and C. velia, being closely related to apicomplexans (Janou skovec et al 2010), can be utilized to speculate how sterols were biosynthesized in apicomplexans before the biosynthetic machinery was lost. A recent study on the sterol composition of C. velia showed the presence of 24R-methylcholesta-5,22Edien-3b-ol, 24R-ethylcholesta-5,22E-dien-3b-ol, and 24-ethylcholest-5-en-3b-ol as major sterols; these three sterols are common in higher plants and seemingly unrelated algae such as chlorarachniophytes (Leblond et al 2005) and glaucocystophytes (Leblond et al 2011).…”

Sterol Composition and Biosynthetic Genes of the Recently Discovered Photosynthetic Alveolate, Chromera velia (Chromerida), a Close Relative of Apicomplexans

“…A comparison to the sterols produced by dinoflagellates as the next closest group with the ability to produce sterols related to C. velia reveals that they do not possess the sterols observed in C. velia [see summary presented by Leblond et al (2010)]. Rather, the identified sterols of C. velia have been observed in other, seemingly unrelated classes of photoautotrophic microalgae, such as chlorarachniophytes (Leblond et al 2005), glaucocystophytes (Leblond et al 2011), and plants as reviewed by Volkman (2003), thus implying that C. velia shares a sterol biosynthesis pathway(s) ancestral to more than one group of algae. With regard to the search for biomarkers in C. velia, because the three identified sterols of C. velia are indeed found in other groups of algae, they are of no biomarker utility to this particular taxon.…”